1. Field of the Invention
The present invention relates to a link connectivity verification method and, in particular, to a link connectivity verification method which verifies connectivity of a physical link between a photonic cross-connect equipment and a transmission equipment which constitute a node of an optical network.
2. Description of the Related Art
A connectivity of a link in a GMPLS optical network including a photonic cross-connect equipment (PXC) can be verified by transmitting an optical signal from one-end side of a target link and receiving the transmitted signal on the other-end side.
FIG. 5 is a conceptual diagram showing a conventional link connectivity verification method. In this case, a simplest 2-node network configuration in an optical network is shown. Two nodes, i.e., nodes 1 and 2 are interposed between client connect equipment A and B. The node 1 (left side in FIG. 5) includes a photonic cross-connect equipment (PXC) 3 and a transmission equipment (to be referred to as a WDM hereinafter) 5 such as a WDM, and the node 2 (right side in FIG. 5) includes a PXC 4 and a WDM 6.
A link connectivity between the PXCs 3 and 4 is verified by externally connecting optical transceivers C and D to the PXCs 3 and 4, respectively and transmitting and receiving an optical signal between the PXCs 3 and 4. For example, an optical signal is transmitted from the optical transceiver C on the PXC 3 side, and the optical signal transmitted through a link is received by the optical transceiver D on the PXC 4 side to verify a link connectivity between the PXCs 3 and 4. This link connectivity verification method is described in IETF RFC4204 Section 5 and IETF RFC4209 Section 2.
However, in the conventional link connectivity verification method, an optical transceiver corresponding to a client signal format of a transmission equipment, for example, SDH (Synchronous Digital Hierarchy), GbE (Gigabit Ethernet (registered trade name)), 10 GbE, or the like is required to verify a link connectivity. When a link connection of an optical network including various client signals is to be verified, optical transceivers coping with various signal formats must be prepared. For this reason, a system having a link connectivity verifying function cannot be economically structured.
In an optical network constituted by PXCs and WDMs, i.e., a so-called Opaque type optical network, it cannot be verified whether a link fault between the PXC and the WDM is occurred or a link fault between the WDM and the WDM is occurred. Since the connectivity fault cannot be distinguished, a rapid and accurate countermeasure cannot be made.